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/* SPDX-License-Identifier: GPL-2.0-or-later */
#include <cpu/power/scom.h>
#include <cpu/power/spr.h> // HMER
#include <console/console.h>
#define XSCOM_DATA_IND_READ PPC_BIT(0)
#define XSCOM_DATA_IND_COMPLETE PPC_BIT(32)
#define XSCOM_DATA_IND_ERR PPC_BITMASK(33, 35)
#define XSCOM_DATA_IND_DATA PPC_BITMASK(48, 63)
#define XSCOM_DATA_IND_FORM1_DATA PPC_BITMASK(12, 63)
#define XSCOM_IND_MAX_RETRIES 10
#define XSCOM_RCVED_STAT_REG 0x00090018
#define XSCOM_LOG_REG 0x00090012
#define XSCOM_ERR_REG 0x00090013
uint64_t read_scom_direct(uint64_t reg_address)
{
uint64_t val;
uint64_t hmer = 0;
do {
/*
* Clearing HMER on every SCOM access seems to slow down CCS up
* to a point where it starts hitting timeout on "less ideal"
* DIMMs for write centering. Clear it only if this do...while
* executes more than once.
*/
if ((hmer & SPR_HMER_XSCOM_STATUS) == SPR_HMER_XSCOM_OCCUPIED)
clear_hmer();
eieio();
asm volatile(
"ldcix %0, %1, %2" :
"=r"(val) :
"b"(MMIO_GROUP0_CHIP0_SCOM_BASE_ADDR),
"r"(reg_address << 3));
eieio();
hmer = read_hmer();
} while ((hmer & SPR_HMER_XSCOM_STATUS) == SPR_HMER_XSCOM_OCCUPIED);
if (hmer & SPR_HMER_XSCOM_STATUS) {
reset_scom_engine();
/*
* All F's are returned in case of error, but code polls for a set bit
* after changes that can make such error appear (e.g. clock settings).
* Return 0 so caller won't have to test for all F's in that case.
*/
return 0;
}
return val;
}
void write_scom_direct(uint64_t reg_address, uint64_t data)
{
uint64_t hmer = 0;
do {
/* See comment in read_scom_direct() */
if ((hmer & SPR_HMER_XSCOM_STATUS) == SPR_HMER_XSCOM_OCCUPIED)
clear_hmer();
eieio();
asm volatile(
"stdcix %0, %1, %2"::
"r"(data),
"b"(MMIO_GROUP0_CHIP0_SCOM_BASE_ADDR),
"r"(reg_address << 3));
eieio();
hmer = read_hmer();
} while ((hmer & SPR_HMER_XSCOM_STATUS) == SPR_HMER_XSCOM_OCCUPIED);
if (hmer & SPR_HMER_XSCOM_STATUS)
reset_scom_engine();
}
void write_scom_indirect(uint64_t reg_address, uint64_t value)
{
uint64_t addr;
uint64_t data;
addr = reg_address & 0x7FFFFFFF;
data = reg_address & XSCOM_ADDR_IND_ADDR;
data |= value & XSCOM_ADDR_IND_DATA;
write_scom_direct(addr, data);
for (int retries = 0; retries < XSCOM_IND_MAX_RETRIES; ++retries) {
data = read_scom_direct(addr);
if ((data & XSCOM_DATA_IND_COMPLETE) && ((data & XSCOM_DATA_IND_ERR) == 0)) {
return;
} else if (data & XSCOM_DATA_IND_COMPLETE) {
printk(BIOS_EMERG, "SCOM WR error %16.16llx = %16.16llx : %16.16llx\n",
reg_address, value, data);
}
// TODO: delay?
}
}
uint64_t read_scom_indirect(uint64_t reg_address)
{
uint64_t addr;
uint64_t data;
addr = reg_address & 0x7FFFFFFF;
data = XSCOM_DATA_IND_READ | (reg_address & XSCOM_ADDR_IND_ADDR);
write_scom_direct(addr, data);
for (int retries = 0; retries < XSCOM_IND_MAX_RETRIES; ++retries) {
data = read_scom_direct(addr);
if ((data & XSCOM_DATA_IND_COMPLETE) && ((data & XSCOM_DATA_IND_ERR) == 0)) {
break;
} else if (data & XSCOM_DATA_IND_COMPLETE) {
printk(BIOS_EMERG, "SCOM RD error %16.16llx : %16.16llx\n",
reg_address, data);
}
// TODO: delay?
}
return data & XSCOM_DATA_IND_DATA;
}
/* This function should be rarely called, don't make it inlined */
void reset_scom_engine(void)
{
/*
* With cross-CPU SCOM accesses, first register should be cleared on the
* executing CPU, the other two on target CPU. In that case it may be
* necessary to do the remote writes in assembly directly to skip checking
* HMER and possibly end in a loop.
*/
write_scom_direct(XSCOM_RCVED_STAT_REG, 0);
write_scom_direct(XSCOM_LOG_REG, 0);
write_scom_direct(XSCOM_ERR_REG, 0);
clear_hmer();
eieio();
}
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